Coal dust furnace



Feb. 7, 1933. G. HAYN GOAL DUST FURNACE Filed Dec. 25, 1928 PatentedFeb. `7, 1933 PATENT foi-FICE GEORG HAYN, or KASSEL, eiiainaivvl i GOALDUST TURNVACE V yApplication,ineapimenter 2s, i928, serial No.` 328,586,mid incermanyianuary' 31, 192g',

The invention relates to coal dust furnaces `more particularlythose'intended for loco- 'motivesand having a burner that'has the Ashape of la spray nozzle.

One of the most difficult problemsin apj plying coal dust furnaces tolocomotives is the realization of a complete combustion under thepeculiar conditions existing in locomotives, that is, the adaptation, asfar aspossible, of the furnace to the usual design of the locomotivecombustion chamber. In comparison with 4'stationary furnaces the maindifficulty with locomotives resides in the fact that in the latter theJcombustion chamber is very small, whilst on 'the other hand the coaldust particles for their complete combustion' require a certain minimumtime, minimum path, and a minimum volume ofl the combustion chamber.These conditions can be vcombined to a minimum value lthat must not bereduced, only if the other conditions are the most favorable* forycombustion. f i

To this end it is necessary that the coal dust particles are mixed Witha sufiicient y quantity of air previous to leaving the burn-f er, inorder that theoxygen required forfthe combustion may be immediately atthe disposal of every coal dust particle. Conven- '30 -iently a portionofthe combustion air, in the mostfofcases the greater part thereof;`this 4depending upon the desired division ofthis air,-is added to the coal dust before the latter entersy the combustion chamber. f Further# 5more, a rapid pre-heating of the coal dust-air mixturel after itsentrance in the combustion chamber has to be providedfor, by radiation,best from the hot brickwork, in order to have the coal dust ignited assoon as possible after mhaving .entered the combustion chamber, to fullyutilize the latter. This requirement may be met .by a suitabledistribution of the mixture in the combustion chamber, by em ploying oneor more burners that are so constructed that they subdivide the mixtureinto a great number of partial jets `and thus in-v crease its surface.With this arrangement individual short thin flames are formed that uniteinto a round flame and completely fill the combustion chamber Withoutsharply striking ther Walls, a premature'destruction of the latter thusbeing avoided. `Finally,

the determinationoffthe average `temperatureof the fire box is ofVimportance, as due l, to `the small sizeof thisv chainberinlocomo- 55tives only afdetermined gasvolume can be f lodged therein, which howeverincreases with increasing temperature. A lowering fof' the temperaturein the lire box andthus a reduction of the gas volume therein howeverre- "6 sults in an increase of thespeciiic load of the iire box, that isan increase of the quantity of heat supplied inthe time unitand spaceunit of the combustion chamber.

If all these favorable conditions are to be fulfilled, it is necessaryto have the igniting zone of the coal dust situated close to the burnerhead Whichythereby in a Very high degreeis exposed to the action of theheat radiated. by the flame. To prevent therefore '7 prematuredestruction of the burner, a water cooling arangementfhasnbeen providedwith knownsfurnaces of this type.V This provi# sionA however involvesboth a very complicated construction and an undesirable in- 275 creaseof Weight, so that With other designs this Water cooling has beenreplaced by an air cooling arrangement. To this end 'a portion of theVcombustion air is 'supplied to the y combustion chamberas so-calledadditional '80 air through passagesthat surround the coal dustsupplying` tube, this cold additional air causing the temperature attheburner head tok be held within admissible limits. I 7 The knownlconstructions'hereinbefore de- 85 scribed however do notconstitute thesimple solution of the problem to be aimed at. Now the object .of mypresentinvention is a coal dust burner that to the largest possibleextent fulfills the required conditions as to simple'construc'tion,sufficient cooling effect and other requirements. This object isobtained by constructing a burner which has a front plate comprising alarge number ofy closely spaced small nozzle-shaped holes; The burnerbody proper therebylies entirely outside the-combustion chamber andbeingy thus cooled by thev outer air remains comparatively 'c old evenwith the highest effect of the n burner, While thenozzle plate whichl isexosed to the radiation of the flame is cooled y the air that conveysthe cold coal dust-air mixture entering the combustion chamber.

As in this manner the quantity of air passing 5 through the nozzle plateis very abundant, this air conveniently being not only coal dustconveying air but also in part combustion air, the temperature of thenozzle plate is held Within such limits that this sensitive burner partis not endangered.

Furthermore, the Haring shape of the nozzles or openings of said burnerplate has a particularly favorable influence upon the cooling of thisplate. For, by the high speed of the cooling means, that is of theconveying and combustion air, at the narrowest or most constricted placeof the nozzle plate not only the necessary reduction of the temperatureof this plate is obtained, but also the iame is prevented from strikingback into the burner body, since it is possible to determine by suitablyshaping the nozzles the speed of the coal dust'air mixture so as toalways be higher than the speed of ignition ofthe mixture. By conicallyenlarging the nozzles toward the combustion chamber, whereby the speedof the mixture is reduced, the condition is fulfilled which is inopposition to the aboveindicated requirement, that the speed of thelconstituents of the mixture should be as low as possible to obtain ashort length of iame.

In order to allow my invention to be more easily understood, a preferredembodiment of the same is illustrated by way of example in the drawingwhich accompanies and forms part of this specification. In this drawingVFigure l is a longitudinal section through the combustion chamber of acoal dust fired locomotive. Y

.Figure 2 is the section on line I--I of Figure l, seen in the directionof the arrows and on an enlarged scale.

The combustion chamber of the coal dust furnace illustrated consists ofa fire box a of usual description and a bottom box b fitted withsuitable brickwork. In the rear, vertical wall of box b are arrangedsymmetrically to the longitudinal middle plane of the engine two burnersc1 and c2. Each of these burners substantially consists of a hollowtruncated conical portion, the smaller rear face of which is connectedto a suitable mixer f for the coal dust-air mixture. These burners aredesigned as spray nozzles, that is their heads are formed by a roseplate d, this plate simultaneously forming a portion of the wall of boxb. In the plates d are provided close together nozzle-shaped holes ewhich may be circular, 'slotted o-r of any other suitable shape andthrough which the coal dust-air mixture is blown into the combustionchamber. For the sake of clearness in Figure 2 these holes e are shownsomewhat greater than they really are. As already mentioned the intimatemixing ofthe two mixture constituents taking part in the combustiontakes place before the burner proper within the mixer f separatelyprovided for each burner and not shown in detail.

The function of the burner and the manner in which it is cooled will beunderstood from the foregoing without further explanation. Owing to thebrickwork being restricted to a minimum extent, the temperature of theiire box can be lowered as mentioned above, because a good heattransmission is obtained by the non-lined water-cooled walls of the lirebox. To inspect or repair the burners, they need only be disconnectedfrom the wall of the box and can then be removed from their seats. Tothis end they are fixed on the wall from outside.

Instead of being arranged on the wall of said lower box, as in theembodiment illustrated, the burners may be disposed at any other placeof the lower box or iire box, according to special constructive pointsof view or conditions of service. Besides as a Inatter of course more orless individual burners may be provided for instead of the two burn- "lers illustrated, as circumstances may require, without deviating fromthe scope of the invention.

What I claim and desire to secure by Letters Patent, is :-u

1. In a coal dust firing installation, a common coal dust and air supplyconduit, a burner in which said conduit terminates, said burner having aface plate provided with a large number of small flaring dischargeopenings adapted to discharge the mixture of coal dust and air, saidopenings being closely spaced with their axes parallel to the axis ofthe burner.

2. In a coal dust ring installation, a common coal dust and air supplyconduit, a burner in which said conduit terminates, said burner having aface plate provided with a large number of small discharge openingsadapted to discharge the mixture of coal dust and air, said openingsbeing closely spaced with their axes parallel to the axis of the burner,and said openings Haring in the direction of flow, thereby permittingexpansion of the mixture and consequent reduction in velocity as it iowsthrough the plate.

The foregoing specification signed at Frankfort-on-the-Main, Germany,this 12th day of December, 1928.

GEORG HAYN.

